So what is support like now?

i've been traveling for the past few days so i was very confused as to why we have irelia bot lane. I just found out that adc's suck now and we can play whatever we want bot lane. as a support main this is kind of confusing. do i still play the champs before the changes? i thought the purpose of support was to guard marksmen because they are generally weaker. now that self sustaining champs can be played bot do i have to stay bot? what's the purpose of support now?
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